Embodiments of the invention relate generally to engines. More particularly, embodiments of the invention relate to systems and methods for controlling an injection of fuel in an engine.
The reduction of fuel expenses and increasing fuel flexibility are some of the objectives in the development of reciprocating engines. Dual-fuel engines have been developed for addressing such objectives. The dual-fuel engines can also provide an advantage of reduced emissions in a dual-fuel combustion mode in comparison to single fuel diesel engines. Typically, a dual-fuel engine can be operated by two fuels: a first fuel and a second fuel. By way of example, the first fuel may include a liquid fuel such as diesel, biodiesel, heavy fuel oil (HFO), or combinations thereof. The second fuel may include a gaseous fuel such as ethanol, natural gas, bio-gas, liquefied petroleum gas, hydrogen, raw gas, associated gas, steel gas, or combinations thereof.
In the dual-fuel combustion mode of the dual-fuel engine, the liquid fuel (e.g., the first fuel) is used to ignite the gaseous fuel (e.g., the second fuel). The benefit of lower fuel costs of the gaseous fuels or lower emissions during the combustion of the gaseous fuels may increase with increasing contribution of the combustion of the gaseous fuels to the overall heat/energy release in dual-fuel combustion mode. The maximization of an energy fraction of the gaseous fuel requires the ability to inject a minimum amount of the first fuel. Moreover, while achieving good combustion stability and a desired cycle to cycle variation target, exact metering of the injected first fuel for the ignition of the second fuel becomes a challenge over the lifetime of the injector. This is in particular the case if only a single injector is used for the injection of the first fuel in the dual fuel operation as well as in a pure first fuel operation.
Therefore, there is a continuous need for improved systems and methods for controlling an injection of fuel in an engine.